ارزیابی خشکسالی و تأثیرات آن بر پوشش گیاهی در مناطق جنوبی ایران

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه سنجش از دور و GIS، دانشکده جغرافیا و علوم محیطی، دانشگاه حکیم سبزواری، سبزوار، ایران

2 گروه ژئومورفولوژی و آب و هواشناسی، دانشکده جغرافیا و علوم محیطی، دانشگاه حکیم سبزواری، سبزوار، ایران

چکیده

تحلیل خشکسالی و پارامترهای متأثر بر آن با استفاده از اطلاعات سنجش از دور توانمندی بالایی برای بهبود دانش علمی در مورد خصوصیات خشکسالی و تأثیرات این پدیده بر روی پوشش گیاهی دارد. تحقیق پیش رو با هدف بررسی ارتباط میان شاخص‌های ماهواره‌ای و شاخص SPI در نواحی جنوبی کشور ایران می‌باشد. بدین منظور ابتدا شاخص SPI در منطقه مورد مطالعه شامل (استان‌های خوزستان، فارس، کهگیلویه و بویراحمد، چهارمحال و بختیاری، بوشهر، هرمزگان و سیستان و بلوچستان) مورد محاسبه قرار گرفت، سپس نقشه‌های پهنه‌بندی با استفاده از مکانیزم پهنه‌بندی کریجینگ تهیه گردید. در مرحله بعد شاخص SPI در منطقه مورد مطالعه مورد محاسبه قرار گرفت، سپس نقشه‌های پهنه‌بندی با استفاده از مکانیزم پهنه‌بندی کریجینگ تهیه گردید. در نهایت به منظور بررسی ارتباط میان شاخص‌های تصاویر ماهواره‌ای با شاخص SPI از ضرایب همبستگی استفاده گردید. پوشش گیاهی طی سال‌های 2008 تا 2017 به میزان قابل توجهی کاهش یافته و به اراضی بایر و یا پوشش گیاهی ضعیف تبدیل شده است. پوشش گیاهی از غرب به شرق منطقه مورد مطالعه کاهش یافته است. در نهایت بین شاخص‌های مذکور همبستگی گرفته شد. نتایج حاصل از همبستگی بیانگر روند کاهشی می‌باشد و بیانگر کاهش میزان پوشش گیاهی با افزایش میزان خشکسالی می‌باشد.

کلیدواژه‌ها


عنوان مقاله [English]

Evaluation of drought and its effects on vegetation in southern regions of Iran

نویسندگان [English]

  • Rahman Zandi 1
  • Alireza Entezari 2
  • Mohammad Baaghide 2
  • Maryam Khosravian 2
1 Department of Remote Sensing and GIS, Faculty of Geography and Environmental Sciences, Hakim Sabzevari University, Sabzevar, Iran
2 Department of Geomorphology and Meteorology, Faculty of Geography and Environmental Sciences, Hakim Sabzevari University, Sabzevar, Iran
چکیده [English]

Introduction
Climate is one of the most important factors affecting vegetation conditions. The spatial distribution of vegetation is closely related to climatic conditions. One of the main features of the Inner Plateau of Iran is its categorization in the dry belt of continental Europe and Asia (Eurasia). This feature and the occurrence of drought due to the unevenness and climate has always had a significant impact on the occurrence of desert characteristics. Drought is the amount of rainfall deviation of one year in a place, compared to the long-term average rainfall in the same place. In areas with low and non-uniform rainfall, the effects of drought are intensive, especially on water resources, agriculture and vegetation. Drought indices are mathematical equations that report drought as a numerical value of one or more variables such as rainfall and evapotranspiration. The purpose of this study was to investigate the changes in vegetation cover in southern Iran (Khuzestan, Fars, Kohgiluyeh and Boyer-Ahmad, Chaharmahal and Bakhtiari, Bushehr, Hormozgan and Sistan and Baluchestan provinces) during the period 2008 to 2017 and its relationship with the drought index in the years studied.
Materials and methods
In this research, MODIS satellite image has been used as an image with low terrestrial resolution and high temporal resolution.
Normalized Differential Plant Index NDVI, is one of the most famous and simple plant indicators used, which is based on two red bands. Near infrared is defined as follows:
NDVI= (NER – RED)/ (NER + RED) 
Standard Precipitation Index (SPI), in this case is the standardized rainfall index used to calculate the probability of rainfall occurrence for all time scales, but is mostly used in the time scales of 1, 3, 6, 12, 24 and 48 months and is one of the most important global indicators for drought.
Discussion and conclusion
The amount of poor vegetation in 2008 was 8302.66 hectares, but in 2017, it decreased to 3436.10 hectares. In general, the average rainfall in the southern regions of the country is 216.03 mm. Studies show that the highest rainfall belongs to Hormozgan province with 326.02 and then Khuzestan and Fars with 305.51 and 286.5 mm respectively and the lowest rainfall, belongs to Kerman and Sistan and Baluchestan provinces with 136.51 and 103.45 mm, respectively. In 2008, southern Iran experienced moderate drought conditions. Drought has been more paramount in Khuzestan, Chaharmahal and Bakhtiari, Kohgiluyeh and Boyer-Ahmad provinces. In some parts of Hormozgan province, drought conditions have been more normal and wet. In 2009, the situation in the whole study area has become more normal and according to the SPI index is close to normal. In order to investigate the amount of vegetation lost, land use changes in the period (2017-2001) were reviewed and the results were presented. According to the results, the vegetation has decreased 138418.4 km from 2008 to 2017 and the amount of agricultural lands has decreased 8155.63 km. Arid land has also increased significantly from 70.9797341 km in 2008 to 2896724.66 km in 2017.
Results
The aim of this study was to investigate the relationship between satellite indices (vegetation parameter) and moving averages of SPI index (climate parameter). According to the results, it can be acknowledged that vegetation parameters have always been affected by climate and parameters affecting it. Therefore, it is certain that in the future, by quantitatively detailed examining of the parameters of vegetation (such as canopy, density, etc.) and climate (such as temperature, humidity, etc.), in the long run, drought warning systems can be established in order to reduce the damage of drought.

کلیدواژه‌ها [English]

  • Drought
  • vegetation
  • Southern regions of Iran
  • Solidarity
-ابراهیم‌زاده، س.و.، بذرافشان، ج. و قربانی، خ.، 1392. امکان سنجی تغییرات گیاهی براساس شاخص­های زمین و ماهواره (مطالعه موردی: استان کرمانشاه)، مجله هواشناسی کشاورزی، شماره‌ 1، ص 37-48.
-مسعودیان، س.ا. و کاویانی، م.ر.، 1387. اقلیم‌شناسی ایران، دانشگاه اصفهان، ۲۴۵ ص.
-میرموسوی، س.ج. و کریمی، ح.، 1392. بررسی تأثیر آنزیمی بر روی گیاهان با استفاده از تصاویر MODIS، مطالعه موردی: کرمانشاه، جغرافیا و توسعه، ص 57-76.
 
 
 
-Agriculture and Natural Resources Research Center, Yazd., 1999. Hydrology and Water Resources Research, Herat. pub, Omran Kavir, 328 p.
-Azim, S., Bharath, B.D. and Kant, Y., 2011. Relation between Land Surface Temperature and Land Use/Land Cover: A Case Study of New Delhi and its Surrounding, development design consultant’s limited Bangladesh. "Satisfactory" on March, 2013.
-Charney, J.G., Quirk, W.J., Chow, S. and Kornfield, J., 1977. A comparative study of the effects of albedo change on drought in the semiarid regions, J. of Atmospheric Sciences, v. 34, p. 136-152.
-Courel, M.F., Kandel, R.S. and Rasool, S.I., 1984. Surface albedo and the Sahel drought. Nature, v. 307, p. 528-531.
-Funk, C. and Budd, M.E., 2009. Phonologically Tuned MODIS NDVI -based production normally estimates for Zimbabwe, Remote Sensing of Environment, 113 p.
-Ichii, K., Kawabata, A. and Yamaguchi, Y., 2002. Global correlation analysis for NDVI and climatic variables and NDVI trends: 1982–1990. International Journal of Remote sensing, v. 23, p. 38-56.
-Karabulut, M., 2003. An examination of relationships between vegetation and rainfall using maximum value composite AVHRR- NDVI data. Turk Journal of Botany, v. 27, p. 93-114.
-Mirmusavi, S.H. and Karimi, H., 2011.  Effects of drought on vegetation using the MODIS images. Journal of Geography and Development v. 31, p. 57-76.
-Rasool, S.I., 1993. Systeme Terre, (France: Dominos Flammarion), 248 p.
-Salimi, M., 2014. Drought Analysis with synthesized index (SDI) and TRMM data in Khorasan Razavi Province, University of Ferdowsi, 362 p.
-Saugier, B., 1996. Vegetation ET atmosphere,), (France: Dominos Flammarion), 107 p.
-Shamsipour, A.A., AlaviPanah, S.K. and Mohammadi, H., 2011. Efficiency of vegetation and thermal indices of NOAA-AVHRR satellite in ecological drought analysis of Kashan region. Iranian Journal of Range and Desert Research, v. 17, p. 44-65.
-Shiravi, M., 2016. Fuzzy Modeling of Desertification Susceptibility of Khorasan Razavi Ecoregions Based on Life Cycle Assessment (LCA). PhD thesis, Ferdowsi University, 84 p.
-Zargar, A., Sadiq, R., Naser, B. and Faisal, K., 2011. A review of drought indices. NRC Research Press Environment, v. 19, p. 33-51.
-Zhaoping, Y., Jixi, G., Caiping, Z., Peili, S., Lin, Z., Wenshou, S. and Hua, O., 2011. Spatio-temporal changes of NDVI and its relation with climatic variables in the source regions of the Yangtze and Yellow rivers, J. Geogr. Sci., v. 21(6), p. 979-993.